The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/net80211/ieee80211_dfs.c

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    1 /*-
    2  * Copyright (c) 2007-2008 Sam Leffler, Errno Consulting
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   24  */
   25 
   26 #include <sys/cdefs.h>
   27 #ifdef __FreeBSD__
   28 __FBSDID("$FreeBSD: stable/11/sys/net80211/ieee80211_dfs.c 343894 2019-02-08 04:48:12Z avos $");
   29 #endif
   30 
   31 /*
   32  * IEEE 802.11 DFS/Radar support.
   33  */
   34 #include "opt_inet.h"
   35 #include "opt_wlan.h"
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h> 
   39 #include <sys/mbuf.h>   
   40 #include <sys/malloc.h>
   41 #include <sys/kernel.h>
   42 
   43 #include <sys/socket.h>
   44 #include <sys/sockio.h>
   45 #include <sys/endian.h>
   46 #include <sys/errno.h>
   47 #include <sys/proc.h>
   48 #include <sys/sysctl.h>
   49 
   50 #include <net/if.h>
   51 #include <net/if_var.h>
   52 #include <net/if_media.h>
   53 #include <net/ethernet.h>
   54 
   55 #include <net80211/ieee80211_var.h>
   56 
   57 static MALLOC_DEFINE(M_80211_DFS, "80211dfs", "802.11 DFS state");
   58 
   59 static  int ieee80211_nol_timeout = 30*60;              /* 30 minutes */
   60 SYSCTL_INT(_net_wlan, OID_AUTO, nol_timeout, CTLFLAG_RW,
   61         &ieee80211_nol_timeout, 0, "NOL timeout (secs)");
   62 #define NOL_TIMEOUT     msecs_to_ticks(ieee80211_nol_timeout*1000)
   63 
   64 static  int ieee80211_cac_timeout = 60;         /* 60 seconds */
   65 SYSCTL_INT(_net_wlan, OID_AUTO, cac_timeout, CTLFLAG_RW,
   66         &ieee80211_cac_timeout, 0, "CAC timeout (secs)");
   67 #define CAC_TIMEOUT     msecs_to_ticks(ieee80211_cac_timeout*1000)
   68 
   69 /*
   70  DFS* In order to facilitate  debugging, a couple of operating
   71  * modes aside from the default are needed.
   72  *
   73  * 0 - default CAC/NOL behaviour - ie, start CAC, place
   74  *     channel on NOL list.
   75  * 1 - send CAC, but don't change channel or add the channel
   76  *     to the NOL list.
   77  * 2 - just match on radar, don't send CAC or place channel in
   78  *     the NOL list.
   79  */
   80 static  int ieee80211_dfs_debug = DFS_DBG_NONE;
   81 
   82 /*
   83  * This option must not be included in the default kernel
   84  * as it allows users to plainly disable CAC/NOL handling.
   85  */
   86 #ifdef  IEEE80211_DFS_DEBUG
   87 SYSCTL_INT(_net_wlan, OID_AUTO, dfs_debug, CTLFLAG_RW,
   88         &ieee80211_dfs_debug, 0, "DFS debug behaviour");
   89 #endif
   90 
   91 static int
   92 null_set_quiet(struct ieee80211_node *ni, u_int8_t *quiet_elm)
   93 {
   94         return ENOSYS;
   95 }
   96 
   97 void
   98 ieee80211_dfs_attach(struct ieee80211com *ic)
   99 {
  100         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  101 
  102         callout_init_mtx(&dfs->nol_timer, IEEE80211_LOCK_OBJ(ic), 0);
  103         callout_init_mtx(&dfs->cac_timer, IEEE80211_LOCK_OBJ(ic), 0);
  104 
  105         ic->ic_set_quiet = null_set_quiet;
  106 }
  107 
  108 void
  109 ieee80211_dfs_detach(struct ieee80211com *ic)
  110 {
  111         /* NB: we assume no locking is needed */
  112         ieee80211_dfs_reset(ic);
  113 }
  114 
  115 void
  116 ieee80211_dfs_reset(struct ieee80211com *ic)
  117 {
  118         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  119         int i;
  120 
  121         /* NB: we assume no locking is needed */
  122         /* NB: cac_timer should be cleared by the state machine */
  123         callout_drain(&dfs->nol_timer);
  124         for (i = 0; i < ic->ic_nchans; i++)
  125                 ic->ic_channels[i].ic_state = 0;
  126         dfs->lastchan = NULL;
  127 }
  128 
  129 static void
  130 cac_timeout(void *arg)
  131 {
  132         struct ieee80211vap *vap = arg;
  133         struct ieee80211com *ic = vap->iv_ic;
  134         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  135         int i;
  136 
  137         IEEE80211_LOCK_ASSERT(ic);
  138 
  139         if (vap->iv_state != IEEE80211_S_CAC)   /* NB: just in case */
  140                 return;
  141         /*
  142          * When radar is detected during a CAC we are woken
  143          * up prematurely to switch to a new channel.
  144          * Check the channel to decide how to act.
  145          */
  146         if (IEEE80211_IS_CHAN_RADAR(ic->ic_curchan)) {
  147                 ieee80211_notify_cac(ic, ic->ic_curchan,
  148                     IEEE80211_NOTIFY_CAC_RADAR);
  149 
  150                 if_printf(vap->iv_ifp,
  151                     "CAC timer on channel %u (%u MHz) stopped due to radar\n",
  152                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  153 
  154                 /* XXX clobbers any existing desired channel */
  155                 /* NB: dfs->newchan may be NULL, that's ok */
  156                 vap->iv_des_chan = dfs->newchan;
  157                 ieee80211_new_state_locked(vap, IEEE80211_S_SCAN, 0);
  158         } else {
  159                 if_printf(vap->iv_ifp,
  160                     "CAC timer on channel %u (%u MHz) expired; "
  161                     "no radar detected\n",
  162                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  163                 /*
  164                  * Mark all channels with the current frequency
  165                  * as having completed CAC; this keeps us from
  166                  * doing it again until we change channels.
  167                  */
  168                 for (i = 0; i < ic->ic_nchans; i++) {
  169                         struct ieee80211_channel *c = &ic->ic_channels[i];
  170                         if (c->ic_freq == ic->ic_curchan->ic_freq)
  171                                 c->ic_state |= IEEE80211_CHANSTATE_CACDONE;
  172                 }
  173                 ieee80211_notify_cac(ic, ic->ic_curchan,
  174                     IEEE80211_NOTIFY_CAC_EXPIRE);
  175                 ieee80211_cac_completeswitch(vap);
  176         }
  177 }
  178 
  179 /*
  180  * Initiate the CAC timer.  The driver is responsible
  181  * for setting up the hardware to scan for radar on the
  182  * channnel, we just handle timing things out.
  183  */
  184 void
  185 ieee80211_dfs_cac_start(struct ieee80211vap *vap)
  186 {
  187         struct ieee80211com *ic = vap->iv_ic;
  188         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  189 
  190         IEEE80211_LOCK_ASSERT(ic);
  191 
  192         callout_reset(&dfs->cac_timer, CAC_TIMEOUT, cac_timeout, vap);
  193         if_printf(vap->iv_ifp, "start %d second CAC timer on channel %u (%u MHz)\n",
  194             ticks_to_secs(CAC_TIMEOUT),
  195             ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  196         ieee80211_notify_cac(ic, ic->ic_curchan, IEEE80211_NOTIFY_CAC_START);
  197 }
  198 
  199 /*
  200  * Clear the CAC timer.
  201  */
  202 void
  203 ieee80211_dfs_cac_stop(struct ieee80211vap *vap)
  204 {
  205         struct ieee80211com *ic = vap->iv_ic;
  206         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  207 
  208         IEEE80211_LOCK_ASSERT(ic);
  209 
  210         /* NB: racey but not important */
  211         if (callout_pending(&dfs->cac_timer)) {
  212                 if_printf(vap->iv_ifp, "stop CAC timer on channel %u (%u MHz)\n",
  213                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  214                 ieee80211_notify_cac(ic, ic->ic_curchan,
  215                     IEEE80211_NOTIFY_CAC_STOP);
  216         }
  217         callout_stop(&dfs->cac_timer);
  218 }
  219 
  220 void
  221 ieee80211_dfs_cac_clear(struct ieee80211com *ic,
  222         const struct ieee80211_channel *chan)
  223 {
  224         int i;
  225 
  226         for (i = 0; i < ic->ic_nchans; i++) {
  227                 struct ieee80211_channel *c = &ic->ic_channels[i];
  228                 if (c->ic_freq == chan->ic_freq)
  229                         c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
  230         }
  231 }
  232 
  233 static void
  234 dfs_timeout(void *arg)
  235 {
  236         struct ieee80211com *ic = arg;
  237         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  238         struct ieee80211_channel *c;
  239         int i, oldest, now;
  240 
  241         IEEE80211_LOCK_ASSERT(ic);
  242 
  243         now = oldest = ticks;
  244         for (i = 0; i < ic->ic_nchans; i++) {
  245                 c = &ic->ic_channels[i];
  246                 if (IEEE80211_IS_CHAN_RADAR(c)) {
  247                         if (ieee80211_time_after_eq(now, dfs->nol_event[i]+NOL_TIMEOUT)) {
  248                                 c->ic_state &= ~IEEE80211_CHANSTATE_RADAR;
  249                                 if (c->ic_state & IEEE80211_CHANSTATE_NORADAR) {
  250                                         /*
  251                                          * NB: do this here so we get only one
  252                                          * msg instead of one for every channel
  253                                          * table entry.
  254                                          */
  255                                         ic_printf(ic, "radar on channel %u "
  256                                             "(%u MHz) cleared after timeout\n",
  257                                             c->ic_ieee, c->ic_freq);
  258                                         /* notify user space */
  259                                         c->ic_state &=
  260                                             ~IEEE80211_CHANSTATE_NORADAR;
  261                                         ieee80211_notify_radar(ic, c);
  262                                 }
  263                         } else if (dfs->nol_event[i] < oldest)
  264                                 oldest = dfs->nol_event[i];
  265                 }
  266         }
  267         if (oldest != now) {
  268                 /* arrange to process next channel up for a status change */
  269                 callout_schedule(&dfs->nol_timer, oldest + NOL_TIMEOUT - now);
  270         }
  271 }
  272 
  273 static void
  274 announce_radar(struct ieee80211com *ic, const struct ieee80211_channel *curchan,
  275         const struct ieee80211_channel *newchan)
  276 {
  277         if (newchan == NULL)
  278                 ic_printf(ic, "radar detected on channel %u (%u MHz)\n",
  279                     curchan->ic_ieee, curchan->ic_freq);
  280         else
  281                 ic_printf(ic, "radar detected on channel %u (%u MHz), "
  282                     "moving to channel %u (%u MHz)\n",
  283                     curchan->ic_ieee, curchan->ic_freq,
  284                     newchan->ic_ieee, newchan->ic_freq);
  285 }
  286 
  287 /*
  288  * Handle a radar detection event on a channel. The channel is
  289  * added to the NOL list and we record the time of the event.
  290  * Entries are aged out after NOL_TIMEOUT.  If radar was
  291  * detected while doing CAC we force a state/channel change.
  292  * Otherwise radar triggers a channel switch using the CSA
  293  * mechanism (when the channel is the bss channel).
  294  */
  295 void
  296 ieee80211_dfs_notify_radar(struct ieee80211com *ic, struct ieee80211_channel *chan)
  297 {
  298         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  299         int i, now;
  300 
  301         IEEE80211_LOCK_ASSERT(ic);
  302 
  303         /*
  304          * If doing DFS debugging (mode 2), don't bother
  305          * running the rest of this function.
  306          *
  307          * Simply announce the presence of the radar and continue
  308          * along merrily.
  309          */
  310         if (ieee80211_dfs_debug == DFS_DBG_NOCSANOL) {
  311                 announce_radar(ic, chan, chan);
  312                 ieee80211_notify_radar(ic, chan);
  313                 return;
  314         }
  315 
  316         /*
  317          * Don't mark the channel and don't put it into NOL
  318          * if we're doing DFS debugging.
  319          */
  320         if (ieee80211_dfs_debug == DFS_DBG_NONE) {
  321                 /*
  322                  * Mark all entries with this frequency.  Notify user
  323                  * space and arrange for notification when the radar
  324                  * indication is cleared.  Then kick the NOL processing
  325                  * thread if not already running.
  326                  */
  327                 now = ticks;
  328                 for (i = 0; i < ic->ic_nchans; i++) {
  329                         struct ieee80211_channel *c = &ic->ic_channels[i];
  330                         if (c->ic_freq == chan->ic_freq) {
  331                                 c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
  332                                 c->ic_state |= IEEE80211_CHANSTATE_RADAR;
  333                                 dfs->nol_event[i] = now;
  334                         }
  335                 }
  336                 ieee80211_notify_radar(ic, chan);
  337                 chan->ic_state |= IEEE80211_CHANSTATE_NORADAR;
  338                 if (!callout_pending(&dfs->nol_timer))
  339                         callout_reset(&dfs->nol_timer, NOL_TIMEOUT,
  340                             dfs_timeout, ic);
  341         }
  342 
  343         /*
  344          * If radar is detected on the bss channel while
  345          * doing CAC; force a state change by scheduling the
  346          * callout to be dispatched asap.  Otherwise, if this
  347          * event is for the bss channel then we must quiet
  348          * traffic and schedule a channel switch.
  349          *
  350          * Note this allows us to receive notification about
  351          * channels other than the bss channel; not sure
  352          * that can/will happen but it's simple to support.
  353          */
  354         if (chan == ic->ic_bsschan) {
  355                 /* XXX need a way to defer to user app */
  356 
  357                 /*
  358                  * Don't flip over to a new channel if
  359                  * we are currently doing DFS debugging.
  360                  */
  361                 if (ieee80211_dfs_debug == DFS_DBG_NONE)
  362                         dfs->newchan = ieee80211_dfs_pickchannel(ic);
  363                 else
  364                         dfs->newchan = chan;
  365 
  366                 announce_radar(ic, chan, dfs->newchan);
  367 
  368                 if (callout_pending(&dfs->cac_timer))
  369                         callout_schedule(&dfs->cac_timer, 0);
  370                 else if (dfs->newchan != NULL) {
  371                         /* XXX mode 1, switch count 2 */
  372                         /* XXX calculate switch count based on max
  373                           switch time and beacon interval? */
  374                         ieee80211_csa_startswitch(ic, dfs->newchan, 1, 2);
  375                 } else {
  376                         /*
  377                          * Spec says to stop all transmissions and
  378                          * wait on the current channel for an entry
  379                          * on the NOL to expire.
  380                          */
  381                         /*XXX*/
  382                         ic_printf(ic, "%s: No free channels; waiting for entry "
  383                             "on NOL to expire\n", __func__);
  384                 }
  385         } else {
  386                 /*
  387                  * Issue rate-limited console msgs.
  388                  */
  389                 if (dfs->lastchan != chan) {
  390                         dfs->lastchan = chan;
  391                         dfs->cureps = 0;
  392                         announce_radar(ic, chan, NULL);
  393                 } else if (ppsratecheck(&dfs->lastevent, &dfs->cureps, 1)) {
  394                         announce_radar(ic, chan, NULL);
  395                 }
  396         }
  397 }
  398 
  399 struct ieee80211_channel *
  400 ieee80211_dfs_pickchannel(struct ieee80211com *ic)
  401 {
  402         struct ieee80211_channel *c;
  403         int i, flags;
  404         uint16_t v;
  405 
  406         /*
  407          * Consult the scan cache first.
  408          */
  409         flags = ic->ic_curchan->ic_flags & IEEE80211_CHAN_ALL;
  410         /*
  411          * XXX if curchan is HT this will never find a channel
  412          * XXX 'cuz we scan only legacy channels
  413          */
  414         c = ieee80211_scan_pickchannel(ic, flags);
  415         if (c != NULL)
  416                 return c;
  417         /*
  418          * No channel found in scan cache; select a compatible
  419          * one at random (skipping channels where radar has
  420          * been detected).
  421          */
  422         get_random_bytes(&v, sizeof(v));
  423         v %= ic->ic_nchans;
  424         for (i = v; i < ic->ic_nchans; i++) {
  425                 c = &ic->ic_channels[i];
  426                 if (!IEEE80211_IS_CHAN_RADAR(c) &&
  427                    (c->ic_flags & flags) == flags)
  428                         return c;
  429         }
  430         for (i = 0; i < v; i++) {
  431                 c = &ic->ic_channels[i];
  432                 if (!IEEE80211_IS_CHAN_RADAR(c) &&
  433                    (c->ic_flags & flags) == flags)
  434                         return c;
  435         }
  436         ic_printf(ic, "HELP, no channel located to switch to!\n");
  437         return NULL;
  438 }

Cache object: f70c4603b76814f25407e184c6984137


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